1. Field of the Invention
The present invention is related generally to an improved composition and method for preparing parenteral formulations comprising solubilized lipophilic pharmaceutical agents and using these formulations in treatment of diseases such as malignant and autoimmune diseases, infectious disorders, or for use in conditioning therapy preceding hematopoietic stem cell transplantation.
2. Description of Related Art
Lipophilic drug substances having low water solubility are a growing class of drugs with increasing applicability in a variety of therapeutic areas for a variety of pathologies. Many compounds approved for pharmaceutical use are lipophilic compounds with limited solubility and bioavailability. Relatively insoluble compounds, i.e., solubility in water of less than 200 μg/mL may show promising pharmaceutical activity, but their development as pharmaceuticals, particularly in parenteral dosage form, present a significant challenge to the pharmaceutical industry. Among the main barriers for effective drug delivery are solubility and stability. To be absorbed in the human body, a compound has to be soluble in both water and fats (lipids). However, solubility in water is often associated with poor fat solubility and vice-versa.
Solubility and stability are, therefore, major obstacles hindering the development of therapeutic agents. Aqueous solubility is a necessary but frequently elusive property for formulations of the complex organic structures found in pharmaceuticals. Traditional formulation systems for very insoluble drugs have involved a combination of organic solvents, surfactants and extreme pH conditions. These formulations are often irritating to the patient and may cause adverse reactions. At times, these methods are inadequate for solubilizing enough of a quantity of a drug for a parenteral formulation.
Therefore, there exists a need for compositions and methods involving formulations comprising solubilized and stable lipophilic pharmaceutical agents, such as busulfan.
As a particular example, the bifunctional DNA-alkylating agent Busulfan (Bu; 1,4-butanediol dimethanesulfonate, aka Butane-1,4-diyl dimetanesulfonate; C6H14O6S2) has over the last several decades earned an impressive reputation for its chemotherapeutic efficacy against numerous malignant diseases. This is most readily appreciated, however, in its activity against myeloid neoplasms, such as that exemplified by chronic myelogenous leukemia (CML) (Haddow and Timmis, 1953; Hoffman et al., 1991).
The therapeutic benefit obtained with Bu in single agent (alkylating agent) therapy in treatment of CML was achieved through its general myelotoxicity. It has lately been increasingly replaced by targeted therapy with tyrosine kinase inhibitors, which may selectively down-regulate the aberrant proliferation of the malignant clone(s) and restore normal polyclonal hematopoiesis.
On the other hand it was recognized by Santos and coworkers, and further refined by Tutschka and coworkers, that the remarkably potent (and selective) myelosuppressive activity of Bu, in addition to its pronounced antileukemic efficacy, makes it an almost ideal agent for use in pretransplant conditioning therapy for patients undergoing hematopoietic stem cell transplantation for malignant-, autoimmune-, or genetic diseases provided that its myelosuppressive activity was paired with the immunosuppressive activity of a second agent, cyclophosphamide (Cy), was usually the preferred “partner” in this setting. Variants of this “Bu-Cy” combination quickly became recognized as (an) acceptable alternative(s) to the (at the time) more commonly used combinations of total body irradiation (TBI) and Cy (Santos and Tutschka, 1974; Santos et al., 1974; Tutschka et al., 1987; Ciurea et al., 2009). When more experience accumulated with the Bu-Cy combinations it became apparent that the unpredictable intestinal absorption and erratic bioavailability of oral Bu was a contributory reason for high peri-transplant morbidity and mortality, most importantly caused by serious liver toxicity or drug-induced toxic hepatitis, clinically referred to as veno-occlusive disease of the liver (VOD). The risk of dying of VOD and other treatment-related complications was reported to be as high as 30-50% already within the first 100 days after the HSCT (Blaise et al., 1992; Devergie et al., 1995; Hartman et al., 1998; Socie et al., 2001; Ciurea et al., 2009). The toxicity from virtually any myeloablative preparative regimen has been associated with the development of VOD (Jones et al., 1987; McDonald et al., 1993; Bearman, 1995), but VOD and/or hepato-renal failure after administration of oral Bu (combined with Cy) has commonly been considered a “trade-mark” toxicity associated with high-dose Bu (both the original BuCy4 [4 days of Cy] and the variant BuCy2 [2 days of Cy] regimens) (Santos et al., 1983; Tutschka et al., 1987; Grochow et al., 1989; Grochow, 1993; Slattery et al., 1997; Dix et al., 1996). Additionally, oral Bu is associated with a hepatic first-pass extraction effect that results in locally high Bu concentrations in the portal-hepatic venous system, and this may contribute to the risk for VOD (Peters et al., 1987). However, in addition to Bu, Cy is clearly hepatotoxic. The findings of McDonald and coworkers suggest that inter-individual differences in metabolic drug handling are of importance for developing VOD, such that, in addition to Bu, Cy conceivably contributes to the overall risk of VOD (McDonald et al., 2003). Thus, the risk of VOD is related to the drug-induced metabolic stress on the liver, especially when both agents depend on hepatic glutathione (GSH) stores and on hepatic Glutathione-S-Transferase (GST) activity for their detoxification (McDonald et al., 2003; Hassan et al., 2000).
In addition to VOD, neurotoxicity was associated with Bu in animals (Deeg et al., 1999). Convulsions in a human receiving oral Bu were first reported by Marcus and Goldman (1984). The incidence of neurotoxicity, especially serious generalized seizure activity, after Bu-based conditioning therapy has been estimated to be as high as 10% in adults (Santos, 1989), and approximately 7% in children (Vassal et al., 1990). Vassal et at reported that higher doses (>600 mg/m2 or 16 mg/kg) are associated with an increased probability of neurotoxic manifestations (Vassal et al., 1989). Seizures are more common in older patients, and they appear to be dose-dependent both in adults and children. Seizures are related to Bu's limited plasma binding and therefore its ability to cross the blood-brain-barrer (Vassal et al., 1990; Vassal et al., 1989; Hassan et al., 1989; Meloni et al., 1992). In adults, seizures typically occur in the 3rd or 4th day of Bu administration, probably as a result of tissue drug accumulation (Marcus and Goldman, 1984; Hassan et al., 1989; Meloni et al., 1992; Kobayashi et al., 1998; Martell et al., 1987; Sureda et al., 1989). Even without overt seizure activity EEG abnormalities occur in up to 60% of patients (Kobayashi et al., 1998). These problems necessitate that various anticonvulsant medications be used for seizure prophylaxis (Meloni et al., 1992; Kobayashi et al., 1998; Grigg et al., 1989; Meloni et al., 1995; Chan et al., 2002; Hassan et al., 1993).
The practical limitations in using oral Bu in high-dose pretransplantation conditioning therapy are primarily related to its unpredictable and erratic bioavailability due to variable intestinal absorption. Available clinical trial data and concerns related to oral Bu toxicity formed the basis for our hypothesis that an IV Bu formulation might cause less stress to the liver, since parenteral administration will yield complete dose assurance with 100% bioavailability as well as circumvent the hepatic first-pass extraction of oral drug that is absorbed from the intestinal tract through the portal-hepatic venous system. This realization prompted the design of an IV Bu formulation to achieve controlled administration (Bhagwatwar et al., 1996; Andersson et al., 2000). The DMA-based IV Bu-formulation was approved by the US FDA in 1999. It has rapidly replaced oral Bu in pre-HSCT chemotherapy, mostly in the IV BuCy2 regimen (Andersson et al., 2002).
So far, IV BuCy2 has been compared with oral BuCy2 in 6 retrospective studies, all showing superiority of IV BuCy2 with regards to the development of VOD and early transplant-related mortality (Kashyap et al., 2002; Thall et al., 2004; Kim et al., 2005; Lee et al., 2005; Aggarwal et al., 2006; Dean et al., 2010). The introduction of IV Bu with Cy appeared to improve the safety of the Bu-Cy(2) regimen(s), however early regimen-related toxicity was/is still of concern. As noted above, it had become apparent through the work of McDonald and coworkers that Cy, when used in high doses in the pretransplant setting, contributed to overall hepatotoxicity (McDonald et al., 1993; McDonald et al., 2003; DeLeve et al., 2002). The activated cytotoxic metabolites of Cy (especially o-carboxyethylphosphoramide mustard and acrolein) likely contribute to VOD in the Bu-Cy2 conditioning regimen through the need for GSH in their metabolic detoxification. As an extension of these observations, the risk for VOD could conceivably be decreased by substituting Cy with an immunosuppressive agent from a different class of drugs without hepatotoxicity, such as Fludarabine (Flu), which does not utilize GSH in its metabolism, and which is virtually non-toxic to the liver. Thus, Russell and colleagues reported on a myeloablative conditioning regimen using IV Bu-Flu and anti-thymocyte globulin (ATG) in a convenient once-daily dosing schedule (Russell et al., 2002). In subsequent, disease-specific studies performed at the M.D. Anderson Cancer Center (MDACC), Flu and IV Bu were also given once daily (De Lima et al., 2004; Andersson et al., 2008). Ninety-six patients with AML/MDS were treated in this study where ATG was added only for matched unrelated donor- and one antigen mismatched sibling donor-transplant patients (De Lima et al., 2004). Stomatitis was commonly seen, and VOD and neurological side effects were still encountered in a fraction of patients. The majority of patients in the first study and 18% in the second study had transient elevations of ALT, while about 10% experienced a significant increase in bilirubin as additional signs of stress on liver function within one to two weeks after transplant (Russell et al., 2002; De Lima et al., 2004). Three of the first 166 (1.8%) patients treated in these two trials developed clinically significant VOD, and one of them died (0.6%). Neurotoxicity was uncommon; 4% of patients developed a “hand-foot” syndrome and two patients had seizures (Russell et al., 2002; De Lima et al., 2004; Andersson et al., 2008). Interestingly, the pattern of liver toxicity appears somewhat different than what was previously experienced with oral Bu; commonly there is a “silent hyperbilirubinemia” in about a third of the patients, having its onset within about a week of IV Bu delivery, and if clinical VOD occurs, it now commonly happens at a later time than what was previously encountered. Thus, clinically diagnosed VOD now occurred in a fraction of patients as late as two months after the HSCT (Andersson, unpublished data).
The parenteral Bu-formulation was developed to achieve 100% bioavailability with complete dose assurance, and to simultaneously eliminate the hepatic first-pass effect which may contribute to the high risk of mortal liver failure after oral high-dose Bu (Bhagwatwar et al., 1996; U.S. Pat. No. 5,430,057; U.S. Pat. No. 5,559,148).
The currently available IV Bu formulation has a composite solvent vehicle based on N,N-Dimethylacetamide (DMA) and Polyethylene-glycol 400 (PEG/PEG400) (“DMA-Bu”) (Bhagwatwar et al., 1996; U.S. Pat. No. 5,430,057; U.S. Pat. No. 5,559,148). Although several clinical studies confirmed that this DMA-Bu formulation is better tolerated and yields improved clinical results of patients transplanted for various types of leukemia and lymphomas (Kashyap et al., 2002; Thall et al., 2004; Kim et al., 2005; Lee et al., 2005; Aggarwal et al., 2006; Dean et al., 2010; DeLeve et al., 2002; Russell et al., 2002; De Lima et al., 2004; Andersson et al., 2008; Chae et al., 2007; Bredeson et al., 2008; Shimoni et al., 2006; Shimoni et al., 2010; Santarone et al., 2011), there was already from the early human trials apprehension about administering a large amount of DMA in humans, since DMA is recognized as a potentially quite toxic solvent (Dwivedi, 2002; VICH Steering Committee, 2010; The Food and Drug Administration, 2010; The Office of Environmental Health Hazard Assessment, 2010). These concerns are justifiably augmented by the possible additive or even synergistic (adverse) interaction(s) between DMA and Bu, since both agents exert significant metabolic stress on the liver. Even though the overall incidence of serious hepatic toxicity is decreased when comparing the oral and IV Bu-Cy2 regimens (Kashyap et al., 2002; Thall et al., 2004; Kim et al., 2005; Lee et al., 2005; Aggarwal et al., 2006; Dean et al., 2010), there is a (sub-) group of patients who suffer serious, life-threatening, or even lethal, hepatic toxicity after receiving the IV Bu-Cy2 and IV Bu-Flu variant regimens (Kashyap et al., 2002; Thall et al., 2004; Kim et al., 2005; Lee et al., 2005; Aggarwal et al., 2006; Dean et al., 2010; Russell et al., 2002; De Lima et al., 2004; Andersson et al., 2008; Chae et al., 2007; Bredeson et al., 2008; Shimoni et al., 2006; Shimoni et al., 2010; Santarone et al., 2011).
It may be important to remember, that the hepatic toxicity profile of IV DMA-Bu is qualitatively somewhat different from that experienced with oral Bu; oral Bu toxicity is manifested as an early, progressive increase in bilirubin, ALT, and AST, typically emerging within the first 10 days following oral Bu administration. This either rapidly progresses to life-threatening or lethal hepato-renal failure or, alternatively the patient starts improving and is clinically significantly better at about 3 weeks after transplantation; the likelihood for complete recovery is now excellent (McDonald et al., 1993; Bearman, 1995; McDonald et al., 2003; DeLeve et al., 2002). In contrast, when the IV DMA-Bu is utilized, there is typically a high (about 30-40%) incidence of “silent hyperbilirubinemia” that appears within 10-14 days following IV DMA-Bu administration. This is likely to resolve in the next several days (up to about a week to ten days), but serious treatment-related hepatic toxicity, VOD, may instead manifest itself as late as 8-10 weeks post-HSCT (Russell et al., 2002; De Lima et al., 2004; Andersson et al., 2008). The inventors hypothesized that the changing clinical toxicity pattern may result from an adverse interaction between Bu and DMA. The latter solvent has demonstrated hepatic, renal and neurologic toxicity in humans, in addition to causing growth retardation and decreased weight gain using rodents and logomorphs in experimental settings (Malley et al., 1995; Kennedy, 1986; Klimisch and Hellwig, 2000; Okuda et al., 2006; Valentine et al., 1997; Kennedy, 2001). In addition, there is at least one report of serious toxic hepatitis with an incidence of about 3-5% in factory workers that were occupationally exposed to high concentrations of vaporized DMA in a commercial plastics production facility (Choi et al., 2001). Finally, in a clinical study of DMA as an anti-cancer agent, the acute, dose-limiting toxicity of DMA was mental confusion/coma, and DMA has also been described as a hallucinogenic agent (Weiss et al., 1962a; Weiss et al., 1962b). The concern about (a) serious adverse interaction(s) between Bu and DMA led one group to investigate the possible clinical adverse interaction(s) when IV DMA-Bu formulation is combined with Cy in pretransplant conditioning therapy (Hempel et al., 2007). These investigators concluded, that although there might be justifiable concerns about (an) adverse interaction(s) between Bu and DMA and Cy, the available IV DMA-Bu formulation is still safer than oral Bu when used in pretransplant conditioning therapy (Hempel et al., 2007). Other investigators demonstrated that under carefully controlled conditions Bu and DMA have a significant (synergistic) cytotoxic interaction (Sadeghi et al., 1999). It is conceivable, that a potentially serious adverse clinical interaction between the two agents is obscured by the naturally occurring interindividual heterogeneity in drug metabolism in the clinical situation. Further, the only comparison that is possible when trying to identify a suitable reference population for evaluation of clinical safety of IV DMA-Bu is the historical comparison with patients treated with oral Bu-based high-dose chemotherapy. Because of the excessively high risk for serious treatment-related complications after high-dose oral Bu, such a comparison will undoubtedly favor DMA-Bu, but it does not address the contribution of DMA to the overall toxicity profile of IV DMA-Bu. Presently such an evaluation is not possible to perform, since the only available IV Bu formulation has a large amount of DMA in the solvent vehicle.
When all available data are considered, it is apparent that inclusion of (a) solvent(s) that impose(s) metabolic stress on the liver, such as DMA, will likely increase the risk for clinically significant liver- and/or multiorgan toxicity, thereby increasing the overall risk to the patient for treatment-regimen related morbidity and mortality. This risk is, however, downplayed by the use of a historical comparator group that was subjected to a significantly worse therapeutic alternative.
The well documented toxicity profile of DMA has rendered it a designation as a Class II agent from the International Cooperation on Harmonization of Technical requirements for Registration of Veterinary Medicinal Products. This designation means that DMA is an agent whose utilization in manufacturing of pharmaceutical formulations should be strictly limited and, if at all possible, it should be avoided (Dwivedi, 2002; VICH Steering Committee, 2010; The Food and Drug Administration, 2010; The Office of Environmental Health Hazard Assessment, 2010).
Therefore, based on the 1) mostly occupational literature reports of serious DMA-induced normal-organ (liver) toxicity, and 2) the acute changes in level of consciousness and/or hallucinations when administered in humans, 3) the occasional later occurring cases of serious, life-threatening as well as lethal, liver toxicity experienced with use of the IV DMA-Bu formulation, and finally 4) the existing FDA-guidelines, there is a need to design an alternative parenteral Bu formulation that is free from DMA. The availability of such a formulation would serve to further improve the clinical safety profile of parenterally administered Bu, such that its full therapeutic potential can be experienced without added concern for serious normal organ toxicity that is imposed by (a) component(s) of the composite solvent vehicle.